This invention relates to an apparatus for splitting, cracking, or fracturing materials by wedging a pointed tool into the material. More particularly, it relates to an apparatus for simultaneously screwing two or more conical wedges into the material to create fracturing or splitting.
Historically, the most common method of splitting a material is by forcing a wedge between the fibers of the material in a plane parallel to the longitudinal axis of the fibers by which the wedge forces the fibers to give up their internal tensions. This invention employs the wedge concept in a conical arrangement.
Whether the wedge is planar in the form of flat surfaces coming together in an edge, such as an ax, or the wedge is a conical screw, the splitting action remains the same. A wedge is forced or driven deeper into the material creating lateral forces that overcome the lateral forces between the fibers of the material releasing their hold on adjacent fibers, so that the material "splits".
In the discussion preceding and following, the workpiece is described with various terminology. In the preferred embodiment the workpiece is wood material, such as logs. However, it should be understood that the operational principles of the apparatus of this invention may be applicable to other materials, particularly if they are fiberous and of a nature similar to wood. In some instances, the apparatus of this invention could be directed to less fiberous and more homogeneous materials such as ceramics and plastics, etc.
In the earliest of times and even in recent years the hand or power ax remains the most common-place type of wood splitting device. However, with the development of more compact rotational power sources the use of rotary conical screw-type wedges have been introduced at least conceptually, if not in extensive practice.
In the conical wedge-type, the progressive driving force carrying the wedge deeper into the material is a helical thread; i.e., a screw progressing deeper as it is rotated.
Typical devices employing single screw helical wedge members are illustrated in the following U.S. Pat. Nos. 953,162--Weinberg, 1,319,656--Merwin, 3,670,789--Thackery, 4,026,337--Thackery, 4,027,709--Thackery.
These single screw devices have the obvious disadvantage that means must be provided to prevent the log material from rotating when the screw is rotated into the material. Various means have been devised to either grasp the log or bar its rotation, but the forces involved are substantial so that the holding means must be substantial also.
More recently, multiple screw devices have been proposed and patented, as disclosed in U.S. Pat. No. 4,252,166--Kozicki and German Patent No. DT2814-249--Hamm.
The Kozicki device discloses a relatively portable construction in which two counter rotating helical screw wedge members are presented to and are driven into the material on parallel rotational axes.
The patent to Hamm is similar except that it relates more specifically to a tractor draw bar or power takeoff type device for mounting on the rear of the conventional vehicle type tractor.